On average 40pc of Great Yarmouth’s youngsters were unhealthily overweight when they started secondary school.

In Waveney 21pc of Year 6 pupils were obese and 4.6pc severely obese.

In King’s Lynn and West Norfolk, and in Breckland, almost one in four of children the same age were obese.

And despite school meals getting healthier the number of obese 10 and 11-year-olds in Year 6 in Breckland rose by 12pc over the last five years - compared to a 4pc rise in King’s Lynn.

Andy Jones Photo: UEA/Andy Jones

But while childhood obesity was a problem for much of England youngsters in Broadland and east Cambridgeshire were some of the healthiest in the country.

Results from Norwich were most stark, underlining the affect of deprivation on weight.

Prevalence among the most deprived Year 6 pupils, which was measured over four years, was at 23pc, while amongst the most affluent it was 19pc.

The results came of little surprise to two Norwich experts.

Professor in public health at the University of East Anglia (UEA), Andy Jones, said one of the challenges was the behaviours that were associated with being overweight.

He said: “They are hard to break in adulthood. We know low cost foods tend to have the most fat in them, the most sugars in them.

“A whole range of changes in society are needed, for example activity. When I was going to school in the 70s and 80s all the children would walk or cycle to school. Now there’s lots of parents dropping them outside in cars. If we are less active we a burning less energy.”

While Dr Jo-anne Veltman, a speciality doctor in diabetes and weight management, at the Norfolk and Norwich University Hospital (NNUH) works within a specialist paediatric team which sees only the most serious of cases.

She said: “The trends are really worrying. It’s not just here, there’s a national state of emergency over obesity. But in terms of the proportion of children we are seeing at young ages who are overweight, it’s extremely worrying. It’s a big problem and it’s affecting a lot of children.”

Dr Veltman said the health impacts on children were vast with some being immediate and others continuing into adulthood.

She said: “When I started in 1992 we were not seeing type two diabetes except in the older adults. As my career has gone on we’ve seen middle-aged people, then in their 20s, and 30s.”

And now she said she’d seen one or two children with the condition.

Almost 90pc of people living with type two diabetes are overweight or obese.

But Dr Veltman said obese and overweight children were also at risk insulin resistance - which comes before diabetes - sleep apnea, which interrupts breathing, and pressure around the brain which in extreme circumstances could cause death.

She also pointed to mental health issues associated with the condition.

She added: “If you don’t do anything about these children and young people the majority of them will be overweight and obese in adulthood.”

Caroline Cerny, lead for the Obesity Health Alliance, described the figures as “startling”.

She said: “We’ve seen a certain amount of progress from government, including the implementation of the soft drinks levy from April this year. But far more needs to be done.”

Miss Cerny called for junk food adverts to be banned while youngsters are watching television.

“They can see up to nine junk food adverts in just 30 minutes while watching their favourite shows,” she said.

“Government must take decisive action to stop children being bombarded with adverts for junk food by introducing a 9pm watershed.”

The government works out obesity using the 1990 British growth reference chart, a large collection of statistics which work out a child’s body mass index (BMI).

It defines a child as obese if its BMI is in the top 5pc, and overweight if they are in the top 15pc. Children’s BMI is measured differently to adults, and is calculated using age and gender as well as height and weight.